ABUJA, Nigeria: Nigeria’s army said three child suicide bombers set off explosions that killed six others and injured at least 24 people.

Army spokesman Col. Sani Kukasheka Usman said Monday that the three were between the ages of 10 and 15 years old. He said they attacked at a security checkpoint on Sunday in Benisheikh, a town in Nigeria’s northeast Borno State.

Usman said the army on Sunday killed at least 12 Boko Haram fighters in an operation in the same state. He said they raided two camps in the operation.

Boko Haram’s 6-year-old uprising has killed an estimated 20,000 people and driven 2.3 million from their homes, according to Amnesty International and the United Nations.

“As part of their determined efforts to rid the society of all known Boko Haram terrorists enclaves and hideouts, troops... conducted a fighting patrol along Damboa-Njaba-Bale road in Borno state” in the northeast of the country, Col. Sani Usman said in a statement.

He said the soldiers “killed three suspected Boko Haram terrorists (who) had been terrorizing the communities around Sabon Gari and Damboa,” on Sunday.

“Among those killed was the Boko Haram terrorist Ameer (leader) in Bulayaga,” he said.